Triplexer systems and methods for use in wireless communications device

ABSTRACT

A wireless communication device is configured for tri-band communication. One of the bands can be for GPS operation. The wireless communication device can comprise an antenna configured to transmit and receive communication signals over two communication bands and to receive GPS signals over a GPS communication band, and a triplexer electrically coupled with the antenna. The triplexer comprises a filter or filters configured to operate at a low frequency band, a filter or filters configured to operate at a mid frequency band, and a filter or filters configured to operate at a high frequency band.

BACKGROUND

1. Field of the Invention

The present invention generally relates to wireless communicationdevices that are configured for operation using a plurality ofcommunication bands and more particularly to GPS enabled multi-bandwireless communication devices.

2. Background Information

A conventional hand-held Global Positioning System (GPS) device providespositional information, related to the location of the GPS device, byreceiving and processing GPS band signals from a GPS system. Althoughsuch positional information can be quite useful, it is not alwaysconvenient to carry a conventional GPS device. Especially, if the usermust also carry around one or more other portable devices, such as alaptop, wireless handset, Personal Digital Assistant (PDA), or otherportable device on which users now depend. It is therefore desirablethat a GPS positioning function be integrated within one of these otherportable devices.

Unfortunately, the integration of GPS technology with other portabledevices has proven difficult. For example, three methods for adding GPScapability to a wireless handset have been implemented, but have provenunsatisfactory in use.

The first method is to add GPS capability in a wireless handset byadding a separate antenna for GPS reception. Since the wireless networkantenna is not modified, network communications quality is not adverselyaffected. However, as mobile handsets for wireless networks have becomemuch smaller, less space is available in the handset housing toaccommodate a separate, custom-designed GPS antenna. Furthermore, a GPSantenna disposed within the handset housing typically suffers from anumber of reception problems. For example, poor reception can be causedby electromagnetic shielding within the handset housing and by thehandset housing itself. Adjusting the electromagnetic shielding toaccommodate the GPS antenna can cause substantial redesign and testingof the handset. Also, adding a separate antenna and its associatedcircuitry to the wireless handset adds expense and design complexity.

The second method is to add GPS capability to a wireless handset byenabling the existing network antenna on the wireless handset toadequately receive a GPS band signal. For example, a typical dual-bandantenna may be constructed to receive a PCS signal at approximately 1900MHz and a cellular signal at approximately 800 MHz. It may therefore bepossible that the existing dual-band antenna may be able to receive aGPS signal at approximately 1575 MHz. However, the GPS signal is at anon-resonant frequency for the dual-band antenna, so the received GPSsignal would be less than optimal resulting in degraded signal transfer.In this regard, known dual-band antenna systems are not able to receivea GPS signal with sufficient strength and quality to implement a robustGPS location functionality on a wireless handset.

The third method is to add GPS capability to a wireless handset using atri-band antenna. A tri-band antenna is constructed to receive thecellular, PCS and GPS frequencies, for example. Due to the limitationsof antenna design, however, such an antenna normally compromises eitherthe cellular or PCS performance, or both. Using a tri-band antenna alsoadds substantial extra cost to the antenna.

SUMMARY OF THE INVENTION

The present invention alleviates to a great extent the disadvantages ofconventional systems and methods for providing a global positioningsystem (GPS) enabled antenna in a wireless communications device, suchas a wireless handset.

In an exemplary embodiment, the present invention provides a system anda method for providing a GPS enabled antenna for a wirelesscommunications device. The wireless communication device includes a GPSswitching module coupled to a conventional communications antenna andassociated circuitry. The GPS switching module is adapted to selectivelycouple the communications antenna to GPS matching circuitry. In thisarrangement, the GPS matching circuitry adjusts impedance atapproximately 1575 MHz to more closely match the communications antennato GPS circuitry in the wireless device, thus ensuring an optimaltransfer of antenna signal energy to the GPS receiver.

These and other features and advantages of the present invention will beappreciated from review of the following detailed description of thepresent invention, along with the accompanying figures in which likereference numerals refer to like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a representation illustrating an exemplary embodiment of awireless communications system according to the present invention;

FIG. 2A shows selected components of an exemplary embodiment of awireless communications device according to the present invention;

FIG. 2B shows selected components of another exemplary embodiment of thewireless communication device of FIG. 2A according to the presentinvention;

FIG. 3A is a plot of a frequency response of a diplexer that can beincluded in the wireless communication device of FIGS. 2A and 2Baccording to an exemplary embodiment of the present invention;

FIG. 3B shows a plot of a frequency response of the diplexer of FIG. 3Aaccording to another exemplary embodiment of the present invention;

FIG. 4 shows selected components of another exemplary embodiment of thewireless communication device of FIG. 2A according to the presentinvention;

FIG. 5 is a plot of a frequency response of a triplexer that can beincluded in the wireless communication device of FIG. 4 according to anexemplary embodiment of the present invention;

FIG. 6 shows an example of a conventional matching network that can beincluded in the wireless communication device of FIG. 2A;

FIG. 7 shows an example of a conventional switching circuit that can beincluded in the wireless communication device of FIG. 2A;

FIG. 8 shows selected components of another embodiment of the wirelesscommunications device of FIG. 2A according to the present invention;

FIG. 9 shows selected components of yet another exemplary embodiment ofthe wireless communications device of FIG. 2A according to the presentinvention;

FIG. 10 shows selected components of an example embodiment of a wirelesscommunication device comprising a triplexer in accordance with theinvention;

FIG. 11 shows selected components of another exemplary embodiment of thewireless communication device illustrated in FIG. 10;

FIG. 12 shows selected components of an example embodiment of a wirelesscommunication device comprising an N-plexer in accordance with theinvention;

FIG. 13 shows selected components of another exemplary embodiment of thewireless communication device illustrated in FIG. 12;

FIG. 14 is a diagram illustrating a graph of the gain and noise figurefor a amplifier that can be included in the wireless communicationdevice of FIG. 13;

FIG. 15 shows selected components of still another exemplary embodimentof the wireless communication device illustrated in FIG. 12; and

FIG. 16 shows selected components of an example embodiment of a wirelesscommunication device comprising single multiport image rejection filterin accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an exemplary embodiment of a wireless communicationssystem including a wireless communication device 100 according to thepresent invention. Wireless communication device 100 can, for example,be a wireless handset, a car phone, a cordless phone, a laptop computeror other computing device with a wireless modem, a pager, or a personaldigit assistance (PDA) with wireless communication capability. Further,wireless communication device 100 can use digital or analog technologyor some combination thereof. Thus, the descriptions below should not beseen as limiting the systems and methods described herein to anyparticular type of wireless communication device.

Wireless communication device 100 includes an antenna 110. Antenna 110is structured to transmit and receive wireless communication signals. InFIG. 1, antenna 110 is in two-way communications with a base station120. Base station 120 can, for example, be one of a plurality of basestations 120 in a wireless communications network. Antenna 110 is alsoin at least one-way communication with one or more GPS satellites, suchas GPS satellite 130. GPS satellite 130 can, for example, be one of aplurality of GPS satellites in a constellation of GPS satellites.

In one example embodiment, wireless communication device 100 is awireless handset having an antenna 110 adapted to receive and transmitwireless communication signals using at least two differentcommunication bands. The two bands can include, for example, thecellular band, a band at approximately 800 MHz, and the PCS band, a bandat approximately 1900 MHz. In this exemplary embodiment, antenna 110 isa conventional dual-band antenna constructed to receive and transmitwireless signals on both the PCS and cellular bands. It will beappreciated that more or fewer communication bands can be accommodatedby appropriate selection of known antennas and associated circuitry. Forexample, wireless communication device 100 can be constructed to useonly the PCS band, or can be constructed to receive and transmit onthree or more communication bands. It will be understood that there aremany communication bands in use throughout the world, and it will befurther understood that the systems and methods described herein are notlimited to any particular communication bands or sets of communicationbands.

Antenna 110 can be a conventional antenna, such as a standard dual-bandantenna. Antenna 110 on wireless communication device 100 is, however,configured to robustly receive position location signals, such as a GPSsignal from satellite 130. Accordingly, GPS position capability can beeconomically and conveniently added to wireless communication device100.

FIG. 2A illustrates a circuit for receiving a GPS signal using aconventional communication antenna 110 in wireless communication device100. Wireless communication device 100 can include, for example, antenna110, a diplexer 140, a first band, e.g., cellular band, duplexer 150, asecond band, e.g., PCS band, duplexer 160, a GPS switching module 170and a GPS module 175. As an alternative to diplexer 140, a two-wayswitch (as illustrated in FIG. 9) can be used. As shown in FIG. 2A,switching module 170 can include, for example, a switch 165. GPS module175 can include, for example, an impedance matching module 180 coupledto a GPS Low Noise Amplifier (LNA) 190. It will be appreciated that thecircuit illustrated in FIG. 2A is for explanation only and thatadditional well-known circuitry must be added to construct a workingwireless communication device 100.

As illustrated in FIG. 2A, antenna 110 is coupled to diplexer 140.Diplexer 140 is coupled to first band duplexer 150. Diplexer 140 is alsocoupled to switching module 170. Switching module 170, in turn, iscoupled to second band duplexer 160. Switching module 170 is alsocoupled to GPS module 175. In an exemplary embodiment, switching module170 is coupled to an impedance matching module 180 within GPS module175, which, in turn, is coupled to GPS LNA 190.

Again, although not shown, additional components can be included in thewireless communication device 100. For example, a GPS signal processorcan be coupled to GPS LNA 190. In another example, transmitters and/orreceivers can be coupled to duplexers 150 and 160. Such additionalcomponents are known and are not described here in detail.

A diplexer is typically used to direct communications signals responsiveto a particular communication band or bands. For example, diplexer 140separates a signal received on antenna 110 into a PCS path or cellularpath. FIG. 3A illustrates an exemplary composite frequency response 200for an exemplary diplexer 140. The frequency response 200 includes a lowpass filter characteristic 210 of a low pass filter included in diplexer140, and a high pass filter characteristic 220 of a high pass filterincluded in diplexer 140. The low pass filter characteristic 210 isillustrated with a cutoff frequency of approximately 1000 MHz and isdesigned to pass the cellular band. The high pass filter characteristic220 is illustrated with a cutoff frequency of approximately 1600 MHz andis designed to pass the PCS band. It will be appreciated that the cutofffrequencies can be adjusted to accommodate particular applications, andthat other cutoff frequencies can be selected for other communicationbands. The high pass filter characteristic 220 can also be designed topass, with some acceptable level of attenuation, a signal in the GPSband.

In operation, wireless communication signals in multiple wirelesscommunication bands, e.g., the cellular and PCS bands, is received byantenna 110. Diplexer 140 splits the wireless communication signals intoa first signal and a second signal. The first signal is filtered by thelow pass filter of diplexer 140 and then coupled to first band duplexer150. The second signal is filtered by the high pass filter of diplexer140 and then coupled to switching module 170. First band duplexer 150can then be configured to couple the first signal to, for example, acellular receiver (not shown). In addition, the low pass filter blockshigher frequency band signals from passing to first band duplexer 150.High pass filter of diplexer 140 passes the second signal to second bandduplexer 160 via switching module 170.

If the multiple received wireless communication signals also include,for example, GPS band signals, then the high pass filter passes, withsome small amount of attenuation, the GPS band signals to GPS module 175via switching module 170. When using a conventional antenna 110, theattenuation is caused, in part, because antenna 110 is not optimized forthe GPS band. In GPS module 175, impedance matching module 180 providesan impedance match that is tuned for the GPS band. GPS signals receivedfrom switching module 170 can then be amplified by GPS LNA 190 beforebeing processed by conventional GPS circuitry (not shown).

The high pass filter of diplexer 140 also blocks lower frequency bandsignals. Wireless communication device 100 operates, in one exampleembodiment, with switching module 170 coupling diplexer 140 to duplexer160. At a selected time or interval, however, it may be desirable toobtain position information. For example, position information can beuseful when a user dials an emergency number. Wireless communicationdevice 100 can also be running an application, such as a mappingapplication, where position is periodically needed. In another example,a user can instruct wireless communication device 100 to obtain positioninformation. It will be appreciated that many applications exist for awireless communication device 100 in which position information isuseful.

When position information is needed, switching module 170 can beswitched by control circuitry (not shown) to couple antenna 110 to GPSmodule 175. When configured in this manner, a GPS band signal atapproximately 1575 MHz can be received by antenna 110 and transmitted toGPS module 175. Since antenna 110 is, for example, a dual-band antennatuned to receive signals at approximately 800 MHz and at approximately1900 MHz, the GPS signal at approximately 1575 MHz is unmatched.Accordingly, matching module 180 includes matching circuitry to moreclosely match the impedance between GPS module 175 and antenna 110 whenit is receiving a GPS signal. As a result, a high quality GPS signal canbe received and forwarded to GPS LNA 190.

In another exemplary embodiment, the composite frequency response 200present in diplexer 140 can be adapted to pass, with less attenuation,the GPS band. Thus, the high pass filter characteristic 220 can bemodified by shifting the cutoff frequency from, for example,approximately 1600 MHz to, for example, approximately 1400 MHz, asillustrated by adapted characteristic 230 in FIG. 3A. The adaptedcharacteristic 230 can also have other differing parameters such as, forexample, a different attenuation slope 235. As a result, the GPS band isattenuated even less by the adapted high pass filter characteristic 230than by the high pass filter characteristic 220. Specifically, forexample, by lowering the cutoff frequency from approximately 1600 MHz(as in normal cellular/PCS diplexer) to approximately 1400 MHz, the GPSband at approximately 1575 MHz is less attenuated by the diplexer 140,e.g., the attenuation can change from approximately −1.3 dB toapproximately −0.3 dB.

FIG. 2B illustrates example components of another example embodiment ofa wireless communication device 100 configured too receive a GPS signalusing a conventional antenna 110. The components are configured in amanner similar to those illustrated in FIG. 2A, except that diplexer 140separates a signal received by antenna 110 into a PCS path and acellular/GPS path. Accordingly, switching module 170 is on thecellular/GPS path. Another example of a frequency response 220 ofdiplexer 140 is illustrated in FIG. 3B. In this example, the low passfilter characteristic 210 of the low pass filter of diplexer 140 extendsto higher frequencies to include the GPS band at approximately 1575 MHz.Accordingly, the low pass filter of diplexer 140 passes the GPS bandsignals or passes the GPS band signals with a small amount ofattenuation to the cellular/GPS path.

FIG. 4 illustrates exemplary components of another example embodiment ofa wireless communication device 100 according to the systems and methodsdescribed herein. In the example embodiment of FIG. 4, wirelesscommunication device 100 can include antenna 110, first band duplexer150, second duplexer 160, GPS module 175, and a triplexer 240. Triplexer240 couples antenna 110 to first band duplexer 150, second band duplexer160, and GPS module 175.

An exemplary frequency response 200 for triplexer 240 is illustrated inFIG. 5 including a low pass filter characteristic 210 of a low passfilter, a high pass filter characteristic 220 of a high pass filter, anda band pass filter characteristic 250 of a band pass filter, allincluded in triplexer 240. The low pass filter characteristic 210 isillustrated with a cutoff frequency of, for example, approximately 1000MHz and is designed to pass, for example, the cellular band. The highpass filter characteristic 220 is illustrated with a cutoff frequencyof, for example, approximately 1600 MHz and is designed to pass, forexample, the PCS band. The band pass filter characteristic 250 iscentered, for example, at approximately 1575 MHz and designed to pass,for example, the GPS band. The characteristics 210, 220, and 250 canoverlap depending on the implementation. Further, other filtercharacteristics designed for these and other wireless communicationbands can be included within triplexer 240 as required by a particularimplementation.

In operation, wireless communication signals are received by antenna110. Triplexer 240 splits the received wireless communication signalinto a first signal, a second signal, and a third signal. If thewireless communication signal includes, for example, cellular bandcommunication signals, then the low pass filter of triplexer 240 passesthe cellular band communication signals to first band duplexer 150. Inaddition, the low pass filter can be configured to block higherfrequency band signals from passing to first band duplexer 150. If thewireless communication signal includes, for example, PCS bandcommunication signals, then the high pass filter passes the PCS bandcommunication signals to second band duplexer 160. In addition, the highpass filter can be configured to block lower frequency band from passingto second band duplexer 160. If the wireless communication signalincludes, for example, GPS band signals, then the band pass filterpasses the GPS band signals to GPS module 175.

GPS module 175, can include an impedance matching module 180 configuredto match the received GPS signal. The GPS signal is then amplified byGPS LNA 190 before being processed by conventional GPS circuitry (notshown). In addition, the band pass filter can be configured to blockhigher and lower frequency bands from passing to GPS module 175.

FIG. 8 illustrated another exemplary embodiment of a wirelesscommunication device 100 in which a switching module 260 is used insteadof triplexer 240. In this example embodiment, antenna 110 is coupled tofirst band duplexer 150, second band duplexer 160, and GPS module 175via switching module 260. Switching module 260 can include, for example,a three-way switch 270. Switching module 260 can be controlled via amain controller (not shown) of wireless communications device 100 suchas, for example, a processor, e.g., a mobile station modem (MSM).

Thus, for example, a cellular band signal can be switched by switchingmodule 260 to first band duplexer 150; a PCS band signal can be switchedto second band duplexer 160; and a GPS signal can be switched to GPSmodule 175. The cellular communications circuitry and the PCScommunications circuitry can include, for example, band-optimized signalmatching circuitry for use with the respective band.

FIG. 9 illustrates yet another exemplary embodiment of wirelesscommunications device 100 configured in accordance with the systems andmethods described herein. In this exemplary embodiment, wirelesscommunication device 100 is configured to receive a GPS signal or acommunication band signal, e.g., a cellular band signal or a PCS bandsignal. Antenna 110 is coupled to GPS module 175 and to communicationband duplexer 290 via a switching module 260. Switching module 260 caninclude, for example, a two-way switch 280. Switching module 260 can becontrolled via a main controller (not shown) of wireless communicationdevice 100 such as, for example, a processor, e.g., a MSM. Switchingmodule 260 switches the signal received via antenna 110 to theappropriate output. Thus, for example, received cellular band signalscan be switched to the communication band duplexer 290. Alternatively, aGPS signal can be switched to GPS module 175. The communication bandcircuitry can include, for example, band-optimized signal matchingcircuitry for use with the communications band.

It will be appreciated that matching module 180 or other matchingcircuitry can be implemented using a wide variety of circuits. FIG. 6illustrates one such implementation of a matching circuit. In FIG. 6, aninput to matching module 180 is coupled to a first inductor L₁ InductorL₁ is coupled to the output of matching module 180 via a second inductorL₂. Inductor L₁ is also coupled to a voltage potential V₁, e.g.,electrical or chassis ground, via a capacitor C₁. Such matching circuitsare well known in the art. Matching module 180 can include other typesof matching circuits and their dual band equivalents. Such matchingcircuits can also include, for example, passive elements.

It will also be appreciated that switch module 170 can be implemented inseveral circuit arrangements. FIG. 7 illustrates one such arrangement ofswitching module 170 according to systems and methods described herein.An input to switching module 170 is coupled to a first capacitor C₂.Capacitor C₂ is coupled to a voltage potential V₂, e.g., battery supplyvoltage, via a first inductor L3. Capacitor C₂ is also coupled to twooutput branches. In a first output branch, capacitor C₂ is coupled to afirst diode D₁. Diode D₁ is coupled to the first output branch via asecond capacitor C₃. Diode D₁ is also coupled to a first control signalvia a second inductor L₄. In a second branch of the circuit, capacitorC₂ is coupled to a second diode D₂. Diode D₂ is coupled to the secondoutput branch via a third capacitor C₄. Diode D₂ is also coupled to asecond control signal via a third inductor L₅.

Briefly, the first control signal and the second control signal providedesired potential differences across the diodes D1 and D2, which turnsdiodes D1 and D2 either on or off, i.e., an approximately short circuitor an approximately open circuit respectively. Switching module 170 cancomprise other variations and examples of switching circuitry as well.

Referring back to FIG. 4, it can be seen that using a triplexer 240reduces the number of components in the receive path for one or more ofthe signals received by antenna 110. This is because using triplexer 240eliminates the need for a switch, such as switching module 170. Reducingthe number of components reduces the circuit board area requirements andlowers the bill of material costs for wireless communication device 100.Eliminating switching module 170 also reduces the insertion loss for thereceive path, which increases the sensitivity and improves theperformance of wireless communication device 100.

One way to implement a triplexer 240 in a wireless communication device100 is illustrated in FIG. 10. Here antenna 110 is coupled to aconventional diplexer, such as diplexer 140. In addition, however,antenna 110 is also coupled with a filter 300 that is configured to actas a band pass filter for signals in the GPS band. In other words,referring to FIG. 5, diplexer 140 in FIG. 10 can be configured toexhibit the low and high pass filter characteristics 210 and 220,respectively, while filter 300 can be configured to exhibit band passfilter characteristic 250.

Conventionally, inductor and capacitor components (L/Cs) have been usedto construct filters with the required characteristics, such as thoseillustrated in FIG. 6. Thus, filter 300 can comprise an L/C filterdesigned to provide band pass filter characteristic 250. Alternatively,such filters can be implemented using Surface Acoustic Wave (SAW)devices. In a SAW device, electrical signals are converted to mechanicalwaves that travel across the surface of the device and are thenconverted back to electrical signals. Thus, filter 300 can also comprisea SAW filter. Similarly, diplexer 140 can be constructed from L/Cfilters or SAW filters.

Triplexer 240 can, therefore, be described as comprising three filtersconfigured to operate at three different frequency bands as illustratedin FIG. 11. As can be seen in FIG. 11, triplexer 240 can comprises afilter 320 configured to operate at a high frequency band, such as thePCS band. Filter 320 can be coupled with a PCS band duplexer 350.Triplexer 240 can also comprise a filter 330 configured to operate at amid frequency band, such as the GPS frequency band. Filter 330 can,therefore, be coupled with GPS receiver circuitry 360. Triplexer 240 canalso comprise a filter 340 configured to operate at a low frequencyband, such as the cellular band. Filter 340 can, therefore, be coupledwith a cellular band duplexer 370.

Again, it should be noted that triplexer 240 can be configured to workin other frequency bands besides the PCS, GPS, and cellular frequencybands. Moreover, the frequency covered by a particular frequency band,such as the PCS and cellular band, can vary depending on the country orcontinent of operation. Thus, triplexer 240 can generically be describedas comprising a high frequency filter 320, a mid frequency filter 330,and a low frequency filter 340.

From a circuit board area perspective, it may be preferable that filters320, 330, and 340 be constructed using L/Cs; however, L/Cs may notprovide enough isolation, or rejection, of other frequency band signals.For example, in the United States, the PCS transmit band is in the high1800 MHz region. The GPS receive band is at approximately 1575 MHz, andthe cellular receive band is in the 800 MHz region. The cellular receiveband is sufficiently distant in terms of frequency from the PCS and GPSreceive bands, such that isolation is not much of a concern. But the PCSand GPS receive bands are relatively close, which makes isolation a morerelevant issue. If there is not enough isolation, then some of theenergy in a received GPS signal can be shunted through PCS filter 320,desensing both the PCS and GPS receivers. Conversely, a portion of areceived PCS signal can be shunted through GPS filter 330 desensing bothreceivers. Thus, if L/Cs are used for filters 320 and 330, it isimportant to ensure that the resulting Quality (Q) factor issufficiently high to provide adequate isolation between the tworeceivers.

In this regard, it may actually be preferable to use SAW filters for oneor both of filters 320 and 330, because SAW filters typically havehigher Qs and provide better isolation. SAW filters, however, arerelatively large compared to simple L/C filter components. Therefore,for each particular implementation, circuit board area and isolationmust be traded off in determining whether to use L/C or SAWs for each offilters 320, 330, and 340. For example, due to the greater need forisolation between a GPS filter 330 and a PCS filter 320, a SAW filtercan be used for filter 330. Because the cellular band is sufficientlydistant from the PCS and GPS bands, however, a lower Q L/C filter can beused for filter 340. Depending on the application, a SAW or L/C filtercan then be used for filter 320. Thus, one or more of filters 320, 330,and 340 can be L/C filters and one or more can be SAW filters, dependingon the tradeoffs and requirements for a particular implementation.

Preferably, however, there would be no need to tradeoff size versusisolation in the design of filters 320, 330, and 340. Fortunately, a newdevice called Film Bulk Acoustic Resonator (FBAR) can be used to achievehigh Q filters with very small footprints. Like SAW devices, FBARdevices convert electrical signals into mechanical waves that resonatethrough the filter material and are then converted back to electricalsignals at the appropriate output. But unlike SAW filters, themechanical waves travel through the body of the material not just acrossthe surface. This allows superior power handling and operation atfrequencies as high as 7.5 Ghz. Moreover, FBAR devices can be madeextremely small.

Therefore, in one embodiment of triplexer 240, each filter 320, 330, and340 is an FBAR filter. In other embodiments, less than all of filters320, 330, and 340 can be FBAR filters depending on the requirements of aparticular implementation.

Accordingly, triplexer 240 allows a single antenna 110 to be used forthree different frequency bands, which eliminates, for example, the needfor a separate GPS antenna. Eliminating the extra antenna reduces thecost of wireless communication device 100, and eliminates the cosmeticand practical disadvantages of including a second antenna in wirelesscommunication device 100. Further, using triplexer 240, as opposed to adiplexer 140 and one or more switching modules 170 also reduces costs,requires less circuit board area, and lowers the insertion loss for oneor more receivers included in wireless communication device 100.Moreover, using FBAR material allows tight integration of the filters320, 330, and 340 comprising triplexer 240, while providing very high Qfilter devices.

In another embodiment, duplexer 350 and 370 (see FIG. 11), are alsointegrated with filters 320, 330, and 340, to form what can be termed anN-plexer. Such an N-plexer 404 is illustrated in FIG. 12, which is alogical block diagram illustrating example components of a wirelesscommunication device 400. Wireless communication device 400 comprises anantenna 402 that is configured to transmit and receive signals in aplurality of communication bands. Antenna 402 is coupled with N-plexer404, which comprises a plurality of filters 406–414.

For example, antenna 402 can be configured to transmit and receive PCSand cellular signals, i.e., device 400 can be configured for dual bandoperation. Wireless communication device 400 can also be configured forGPS operation, in which case filters 406–414 can be grouped into threecommunication ports. One communication port 428 can be configured as aPCS communication port and can comprise filters 406 and 408. Filter 406can in turn be configured to receive PCS transmit signals via transmitsignal line 416 from a PCS transceiver (not shown) also included inwireless communication device 400. The PCS transmit signals are thenpassed to antenna 402 for transmission. Filter 408, on the other hand,can be configured to receive PCS receive signals from antenna 402 andpass them, via receive signal line 418 to the PCS transceiver (notshown).

Filters 406 and 408 can be configured as bandpass filters that passsignals within the PCS transmit and receive bandwidths, respectively. Inaddition, filters 406 and 408 can be configured to provide isolationbetween the PCS transmit and receive paths 416 and 418, so that they donot interfere with each other and are isolated from signals in othercommunication bands, e.g., the GPS and cellular bands.

Similarly, a cellular communication port 430 can comprise filters 412and 414. Filters 412 and 414 can, therefore, be configured to passtransmit and receive cellular signals, respectively, between antenna 402and a cellular transceiver (not shown) via signal paths 424 and 426,respectively. Further, filters 412 and 414 can be configured to provideisolation relative to signals outside of the transmit and receivecellular bandwidths.

Filter 410 can be configured to pass GPS receive signals received byantenna 402 to GPS receive circuitry 422 via receive signal path 420.Filter 410 can also be configured to provide isolation from signalsoutside the GPS receive bandwidth.

Accordingly, N-plexer 404 can be configured to replace the combinationof triplexer 240 and duplexers 350 and 370. This not only reduces thenumber of components required, but also reduces the insertion loss forthe various transmit and receive signal paths. Of course, N-plexer 404can be configured for other communication bands. Further, a fourth,fifth, etc. signal port can be added to N-plexer 404 as required by aspecific wireless communication device 400. Therefore, N-plexer 404should not be viewed as being limited to a certain number ofcommunication ports or to implementations involving specificcommunication bands.

As described with respect to triplexer 240, filters 406–414 can compriseL/Cs or SAW devices as required by a particular application. From acircuit board area standpoint, L/Cs may be preferable to SAW devices,but SAW devices typically provide more isolation and higher Qs.Preferably, however, FBAR devices are used for each of the filterdevices 406–414. This is because FBAR provides high isolation, high Q,and a small footprint, which not only makes it easier to implementN-plexer 404, but also makes it easier to add additional communicationports to N-plexer 404 if required.

In FIG. 13, it can be seen that including an N-plexer 504 in a wirelesscommunication device 500, which is configured for dual bandcommunication and GPS operation for example, reduces the number ofcomponents between antenna 502 and the receive circuits 512, 514, and516. Thus, the insertion loss is reduced as well as the component count.Further, if N-plexer 504 is constructed from FBAR material, then theoverall circuit board area requirement can also be reduced.

In FIG. 13, the receive paths 506, 508, and 510 for three communicationports included in N-plexer 504 are illustrated. Thus, receive path 506can be a PCS receive path, receive path 508 can be a GPS receive path,and receive path 510 can be a cellular receive path. Receive path 506 isthen coupled with an amplifier 512 that comprises a part of a PCSreceiver included in wireless communication device 500. Similarly,receive paths 508 and 510 will be coupled with amplifiers 514 and 516,which comprise part of a GPS receiver and a cellular receiver,respectively, included in wireless communication device 500.

Amplifiers 512, 514, and 516 are generally LNAs. LNAs are key componentsin Radio Frequency (RF) receivers because they take received signals,which are typically at very low power levels, and amplify them to alevel sufficient for further processing without adding additional noisethat may mask or distort the low power received signals. In aconventional wireless communication device, each receive path has acorresponding LNA that is configured for optimal performance over thefrequency band associated with the particular receive path. But sincethe diplexers, switches, and duplexers can be reduced to a single device504, it would be advantageous to be able to use a single LNA for two ormore receive paths, especially where the communication bands associatedwith the receive paths are close, such as with the PCS and GPS bands.

To obtain the best Noise Figure (NF) for a conventional LNA, it is oftenbest to provide a termination impedance of approximately 90 ohms.Unfortunately, the output of most filter devices that interface with anLNA is 50 ohms. This includes most conventional diplexers and duplexers,as well as most embodiments of triplexer 240 and N-plexer 504. Providinga 50 ohm impedance instead of a 90 ohm impedance lowers the LNA input Qand broadens the LNA pass band. This can be illustrated with the use ofthe curves graphed in FIG. 14. In FIG. 14, curve 630 illustrates thegain curve for an LNA when the input impedance is 90 ohms. Thus, thegain in decibels (dB) is graphed against the frequency in Hertz (Hz). Itcan be seen that the LNA has a relatively narrow pass band centered atapproximately 1.5 GHz in the example of FIG. 14. Curve 632 graphs thecorresponding NF, which is relatively good over the pass band.

When, however, a 50 ohm input impedance is used, gain curve 636 and NF634 are obtained. As can be seen, the pass band for curve 636 isbroadened, but the gain across the pass band is reduced. The NF 634 isalso somewhat degraded across the pass band. Fortunately, even when thelower gain and degraded NF are taken into account, the wider pass bandcan be taken advantage of to allow a single LNA to be used for more thanone receive path, especially where the associate receive bandwidths arerelatively close.

In FIG. 15, for example, a PCS receive path 706 and a GPS receive path708 are both coupled over a single receive signal path 710 with a singleLNA 714 in wireless communication device 700. As explained above, theimpedance of signal path 710 is 50 ohms. Wireless communication device700 can also comprise, for example, a cellular receive path 712interface with a LNA 716. Each receive path 706, 708, and 712 can, forexample, comprise part of a corresponding communications port in aN-plexer 704, which in turn is interfaced with antenna 702.

Because the impedance of signal path 710 can be 50 ohms, a broader passband can be obtained for LNA 714 that can, for example, be broad enoughfor use at both the GPS receive band and the PCS receive band. Thus, forexample, by simply using a 50 ohm termination, LNA 714 can be configuredfor dual use on both PCS and GPS signals. Further, the loss in gain anddegraded NF in each receive band can be counter balanced by lowering theinsertion loss using, for example, N-plexer 704. Accordingly, a LNA 714with a pass band centered at the PCS receive band can be used for bothPCS and GPS signals. Alternatively, a LNA 714 with a pass band centeredat the GPS receive band can be used for both signals, or a LNA 714 witha pass band somewhere in between the GPS and PCS receive bands or closeto one or the other can be used.

The reuse of a single LNA is not limited to reusing the LNA for only tworeceive paths. For example, a LNA centered at 1.5 GHz and with a passband such as that illustrated by curve 634 in FIG. 14 can be used forPCS signals, GPS signals, and cellular signals. Thus, as illustrated inFIG. 16, a wireless communication device 800 can comprise an antenna 802configured to transmit and receive signals in a plurality ofcommunication bands, an N-plexer 804 comprising a plurality ofcommunication ports, and a single LNA 806 configured to amplify receivesignals for two or more of the communication bands.

If, for example, antenna 802 is configured to receive PCS, GPS, andcellular signals, then N-plexer 804 can comprises a PCS, GPS, andcellular communication port. LNA 806 can then be used to amplifyreceived PCS, GPS, and cellular signals. Further, because N-plexer 804is used, which reduces the insertion losses, the lower gain and degradedNF that results from using single LNA 806 can be counter balanced. Thecenter of the pass band of LNA 806 can also be adjusted if required toincrease the gain for a particular band, e.g., the center frequency canbe shifted down to get more gain in the cellular band if required by aparticular application.

Wireless communication device 800 can also include image rejectionfilter 808. In a conventional receiver, an image rejection filtertypically follows the LNA. The image rejection filter is configured toreduce, among other things, the noise and response in the image band sothat the noise response does not interfere with proper reception of areceived signal. Thus, in a wireless communication device configured toreceive signals in a plurality of communication bands, a discrete imagerejection filter would be required for each communication band. But inorder to reduce the number of components, a single image rejectionfilter 808 can be configured to filter signals for each communicationband received by wireless communication device 800.

Thus, for example, image rejection filter 808 can comprise three signalports: one configured to filter PCS signals, one configured to filterGPS signals, and one configured to filter cellular signals. Each signalport preferably comprises a FBAR filter device, but can comprise filtersconstructed using L/Cs and/or SAW devices as is the case for N-plexer804.

Accordingly, by implementing the systems and methods described above, awireless communication device 800 configured to receive signals in aplurality of communication bands can comprise a single antenna 802, asingle N-plexer 804, a single LNA 806, and a single image rejectionfilter 808. Alternatively, partial integration at the N-plexer, LNA,and/or image rejection filter stages, according to the systems andmethods described herein, can still be implemented to reduce componentcounts, circuit board area requirements, and cost. Thus, for example, adual band, GPS enabled, wireless communication device can be made verysmall and inexpensive. Although, as previously mentioned, the systemsand methods described herein are not limited to particularimplementations or to use with any specific communication bands.

Therefore, while embodiments and implementations of the invention havebeen shown and described, it should be apparent that many moreembodiments and implementations are within the scope of the invention.Accordingly, the invention is not to be restricted, except in light ofthe claims and their equivalents.

1. A triplexer for use in a wireless communication device, the triplexerincluded in a single component comprising a single device, the singledevice triplexer comprising: an antenna interface; a first communicationport, coupled internal to the single component with the antennainterface, comprising a filter configured to operate at a low frequencyband and to communicate at least one of a transmit signal and a receivesignal with an antenna through the antenna interface, wherein the lowfrequency band corresponds to a cellular frequency band; a secondcommunication port, coupled internal to the single component with theantenna interface, comprising a filter configured to operate at a midfrequency band and to communicate at least one of a transmit signal anda receive signal with the antenna through the antenna interface, the midfrequency band corresponding to a GPS frequency band; and a thirdcommunication port, coupled internal to the single component with theantenna interface, comprising a filter configured to operate at a highfrequency band and to communicate at least one of a transmit signal anda receive signal with the antenna through the antenna interface.
 2. Thetriplexer of claim 1, wherein the triplexer is constructed from FBARmaterial.
 3. The triplexer of claim 1, wherein the high frequency bandcorresponds to a PCS frequency band.
 4. The triplexer of claim 1,wherein the first communication port comprises a first filter configuredto transmit signals to the antenna and a second filter configured toreceive signals from the antenna.
 5. The triplexer of claim 4, whereineach of the filters associated with the first communication port isfurther configured to isolate the associated transmit and receive signalfrom each other.
 6. The triplexer of claim 5, wherein each of thefilters associated with the first communication port is furtherconfigured to reject signals associated with the other filters.
 7. Thetriplexer of claim 1, wherein the second communication port comprises afirst filter configured to transmit signals to the antenna and a secondfilter configured to receive signals from the antenna.
 8. The triplexerof claim 7, wherein each of the filters associated with the secondcommunication port is further configured to isolate the associatedtransmit and receive signal from each other.
 9. The triplexer of claim8, wherein each of the filters associated with the second communicationport is further configured to reject signals associated with the otherfilters.
 10. The triplexer of claim 1, wherein the third communicationport comprises a first filter configured to transmit signals to theantenna and a second filter configured to receive signals from theantenna.
 11. The triplexer of claim 10, wherein each of the filtersassociated with the third communication port is further configured toisolate the associated transmit and receive signal from each other. 12.The triplexer of claim 11, wherein each of the filters associated withthe third communication port is further configured to reject signalsassociated with the other filters.
 13. A wireless communication device,comprising: an antenna configured to communicate signals in threecommunication bands; and a triplexer electrically coupled with theantenna, the triplexer included in a single component, the triplexercomprising: an antenna interface configured to interface the triplexerwith the antenna; a first communication port, coupled internal to thesingle component with the antenna interface, comprising a filterconfigured to operate at a low frequency band and to communicate atleast one of a transmit signal and a receive signal with the antennathrough the antenna interface, wherein one of the communication bandscorresponds to a cellular band; a second communication port, coupledinternal to the single component with the antenna interface, comprisinga filter configured to operate at a mid frequency band and tocommunicate at least one of a transmit signal and a receive signal withthe antenna through the antenna interface; and a third communicationport, coupled internal to the single component with the antennainterface, comprising a filter configured to operate at a high frequencyband and to communicate at least one of a transmit signal and a receivesignal with the antenna through the antenna interface, one of thecommunication bands corresponding to the GPS band.
 14. The wirelesscommunication device of claim 13, wherein the triplexer is constructedfrom FBAR material.
 15. The wireless communication device of claim 14,wherein the first communication port further comprises a first filterconfigured to transmit signals to the antenna and a second filterconfigured to receive signals from the antenna.
 16. The wirelesscommunication device of claim 15, wherein each of the filters associatedwith the first communication port is further configured to isolate theassociated transmit and receive signal from each other.
 17. The wirelesscommunication device of claim 16, wherein each of the filters associatedwith the first communication port is further configured to rejectsignals associated with the other filters.
 18. The wirelesscommunication device of claim 14, wherein the second communication portfurther comprises a first filter configured to transmit signals to theantenna and a second filter configured to receive signals from theantenna.
 19. The wireless communication device of claim 18, wherein eachof the filters associated with the second communication port is furtherconfigured to isolate the associated transmit and receive signal fromeach other.
 20. The wireless communication device of claim 19 whereineach of the filters associated with the second communication port isfurther configured to reject signals associated with the other filters.21. The wireless communication device of claim 14, wherein the thirdcommunication port further comprises a first filter configured totransmit signals to the antenna and a second filter configured toreceive signals from the antenna.
 22. The wireless communication deviceof claim 21, wherein each of the filters associated with the thirdcommunication port is further configured to isolate the associatedtransmit and receive signal from each other.
 23. The wirelesscommunication device of claim 22, wherein each of the filters associatedwith the third communication port is further configured to rejectsignals associated with the other filters.
 24. The wirelesscommunication device of claim 13, wherein one of the communication bandscorresponds to a PCS band.
 25. The wireless communication device ofclaim 13, wherein the first communication port further comprising afilter configured to transmit signals to the antenna and a second filterconfigured to receive signals from the antenna.
 26. The wirelesscommunication device of claim 25, wherein each of the filters associatedwith the first communication port is further configured to isolate theassociated transmit and receive signal from each other.
 27. The wirelesscommunication device of claim 26, wherein each of the filters associatedwith the first communication port is further configured to rejectsignals associated with the other filters.
 28. The wirelesscommunication device of claim 13, wherein the second communication portfurther comprising a filter configured to transmit signals to theantenna and a second filter configured to receive signals from theantenna.
 29. The wireless communication device of claim 28, wherein eachof the filters associated with the second communication port is furtherconfigured to isolate the associated transmit and receive signal fromeach other.
 30. The wireless communication device of claim 29, whereineach of the filters associated with the second communication port isfurther configured to reject signals associated with the other filters.31. The wireless communication device of claim 13, wherein the thirdcommunication port further comprising a filter configured to transmitsignals to the antenna and a second filter configured to receive signalsfrom the antenna.
 32. The wireless communication device of claim 31,wherein each of the filters associated with the third communication portis further configured to isolate the associated transmit and receivesignal from each other.
 33. The wireless communication device of claim32, wherein each of the filters associated with the third communicationport is further configured to reject signals associated with the otherfilters.